

class MyLinkedList {
    static class ListNode{
        public ListNode prev;
        public ListNode next;
        public int val;
        public ListNode(int val){
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else{
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    public void display() {
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
    }

    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = node;
            last = node;
        }else{
            last.next = node;
            node.prev = last;
            last = last.next;
        }
    }
    //得到单链表的长度
    public int size() {
        ListNode cur = head;
        int count = 0;
        while (cur != null) {
            cur = cur.next;
            count++;
        }
        return count;
    }
    //查找index下标数据并返回结点
    private ListNode findIndexdData(int index){
        ListNode cur = head;
        while(index != 0){
            cur = cur.next;
            index--;
        }
        return cur;
    }
  //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index, int data) {
        if(index < 0 || index > size()){
            throw new IndexOutOfBoundsException();
        }
        ListNode node = new ListNode(data);
        //头插
        if(index == 0){
            addFirst(data);
        }
        //尾插
        else if(index == size()){
            addLast(data);
        }
        //中间
        else{
            ListNode cur = findIndexdData(index);
            node.next = cur;
            node.prev = cur.prev;
            cur.prev.next = node;
            cur.prev = node;
        }
        return true;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                if(cur == head){
                    head = cur.next;
                    head.prev = null;
                    cur = head;
                    return;
                }
                else if(cur == last){
                    last = cur.prev;
                    cur = last;
                    cur.next = null;
                    return;
                }
                else{
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                    cur = cur.next;
                    return;
                }
            }
            cur = cur.next;
        }
        System.out.println("未找到该节点!");
    }
    //删除所有值为key的节点
    public void removeAllKey(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                if(cur == head){
                    head = cur.next;
                    head.prev = null;
                }
                else if(cur == last){
                    last = cur.prev;
                    last.next = null;
                }
                else{
                    cur.prev.next = cur.next;
                    cur.next.prev = cur.prev;
                }
            }
            cur = cur.next;
        }
    }
    public void clear() {
        while(head.next != null){
            head = head.next;
            head.prev.prev = null;
            head.prev.next = null;
        }
        head.prev = null;
        head = null;
        last = null;
    }
}
